The present invention is directed to the use of polycondensation products which are produced by the condensation of acrolein and formaldehyde in a molar ratio between 1:1 and 1:10 in aqueous or aqueous-organic medium in the presence of a basic catalyst as biocides for aqueous systems.
It is already known to use acrolein as a biocide for aqueous systems, for example, to prevent growth of algae in water circulation and to reduce the biological bacterial count. The biocide effectiveness of acrolein indeed is good, its use, however, also has considerable disadvantages, above all, because of its extraordinarily pungent odor even in the slightest concentration and on account of its low flash point. Also there is considerable difficulty in distributing small amounts of acrolein homogeneously in water within a short time even though acrolein is soluble to about 18% in water.